Systems and methods for overlay shift determination

ABSTRACT

The systems and methods enable the determination of the magnitude and direction of overlay of at least two elements in two layers. Overlay measurements along two axes can be obtained using four probe pads and without requiring a decoder. Overlay measurements along a single axis can be obtained using three probe pads and without requiring a decoder. The systems and methods according to this invention require less space and are more time efficient than conventional measurement structures. In the systems and methods of this invention, offsets in a direction are calculated from resistance measurements.

BACKGROUND OF INVENTION

This invention relates to systems and methods for overlay shiftdetermination, and in particular, to systems and methods for determiningthe magnitude and direction of an error in the alignment of at least onefirst layer with at least one second layer of a semiconductor device.

Semiconductor devices are manufactured with a plurality of differentlayers and a plurality of different processing steps, such as, forexample, masking, resist coating, deposition and etching. During thesemiconductor manufacturing process, many materials are provided on thesemiconductor device and portions of the provided materials are removedby etching, for example, in order to form elements of the integratedcircuit. For example, circuit elements are formed using patterned maskswhich expose and protect respective regions of various layers to form anintegrated circuit. These patterned masks, for example, should besubstantially, and ideally completely, aligned with the respectivelayer.

Ideally the respective layers and/or patterned masks of an integratedcircuit, for example, are perfectly aligned. However, perfect alignmentis difficult, and nearly impossible to achieve. Errors in the alignmentof one layer with another layer during the manufacturing process ofsemiconductor devices can occur for a wide-variety of reasons. Forexample, errors made during the manufacturing process may occur as aresult of alignment noise, stage scanning problems, lens distortions,and wafer stage inaccuracies.

The performance of the semiconductor device, however, depends on theproper alignment of the patterned masks with each of the layers formingthe semiconductor device. As integrated circuits become smaller andsmaller the proper alignment between layers becomes even more important.If the layers and/or masks for forming the semiconductor device and theintegrated circuits formed thereon are not aligned properly, thesemiconductor device may fail to operate properly, if at all.

There are a variety of known methods for detecting the misalignmentbetween layers of semiconductor devices. By way of example, it is knownto use resistance based alignment for magnetoresistive elements, wherethe sheet resistivity of each of the two alignment test structures isused to detect the misalignment of the elements. However, these types ofdesigns require large structures and are dependent on processingvariations. Other methods include ways to determine if the openingslocated in the contact layer and the interconnect layer are misaligned.However, these methods do not determine the direction or the magnitudeof the misalignment.

In still other methods, mask-alignment test structures are used formeasuring the alignment of superimposed elements formed on and within asemiconductor element. In order to determine the magnitude and extent ofmisalignment in both the X and Y directions, for example, in thesemethods, it is necessary to have four of the structures disclosed.Further, in order to determine the magnitude and extent of themisalignment in accordance with such methods approximately sixteen stepsand seven probe pads are required in the case where a decoder is notused and approximately four steps and ten probe pads are required in thecase where a decoder is used. Thus, such devices are large in sizeand/or time consuming due to the number of steps required to determinethe magnitude of the misalignment. This is time consuming and costly. Itis also known to use optical methods to determine error in misalignment.However, optical methods for determining error in misalignment aregenerally slower than electrical test structures.

SUMMARY OF INVENTION

In an aspect of the invention, an overlay shift determination structurehas a plurality of probe members in a first layer and an overlay targetin a second layer of an integrated device. At least a portion of theplurality of probe members overlaps and is connected to the overlaytarget and the first layer includes a first axis and a second axis whichis perpendicular to the first axis. A first probe member and a secondprobe member of the plurality of probe members are disposed along afirst axis and a third probe member of the plurality of probe members isdisposed perpendicular to the first probe member and the second probemember.

In another aspect of the invention, a method is provided for measuringmisalignment between at least two layers of an integrated circuit byapplying a current between a plurality of probe members in a first layerwhere a first probe member and a second probe member of the plurality ofprobe members are substantially aligned along a first axis and partiallyoverlap an overlay target in a second layer. The method measures avoltage across the plurality of probe members where at least a voltageacross the first probe member and a third probe member which is disposedperpendicular to the first axis and a voltage across the second probemember and the third probe member are measured. The method furtherdetermines an amount of misalignment between the first layer and thesecond layer along at least one of the first axis and the second axisbased on the measuring steps.

In another aspect, the invention provides a computer program productcomprising a computer usable medium having readable program codeembodied in the medium, the computer program product includes a firstcomputer program code for applying a current between a plurality ofprobe members in a first layer, wherein at least two of the probemembers are aligned along a first axis and partially overlap an overlaytarget in a second layer, a second computer program code for measuring avoltage across the plurality of probe members where the measured voltageis between at least one of the two aligned probe members and a thirdprobe member disposed perpendicular to the first axis, and a thirdcomputer program code for determining an amount of misalignment betweenthe first layer and the second layer along at one of the first axis andthe second axis based on the measured voltages.

BRIEF DESCRIPTION OF DRAWINGS

Various exemplary embodiments of this invention will be described indetail with reference to the following figures, wherein:

FIG. 1 illustrates an aligned embodiment of an overlay shiftdetermination structure according to this invention;

FIG. 2 illustrates a cross-sectional view along line II—II of theoverlay shift determination structure shown in FIG. 1;

FIG. 3 illustrates a cross-sectional view along line III—III of theoverlay shift determination structure shown in FIG. 1;

FIG. 4 illustrates an exemplary embodiment of an overlay shiftdetermination structure according to this invention;

FIG. 5 illustrates a cross-sectional view along line V—V of the overlayshift determination structure shown in FIG. 4;

FIG. 6 illustrates a cross-sectional view along line VI—VI of theoverlay shift determination structure shown in FIG. 5;

FIG. 7 illustrates an improperly aligned overlay shift determinationstructure according to the embodiment of this invention;

FIG. 8 illustrates a cross-sectional view along line VIII—VIII of theimproperly aligned overlay shift determination structure shown in FIG.7;

FIG. 9 illustrates a cross-sectional view along line IX—IX of theimproperly aligned overlay shift determination structure shown in FIG.7;

FIG. 10 illustrates schematic views of an overlay shift determinationstructure according to this invention;

FIG. 11 illustrates a flow-chart outlining a method for determining anoverlay shift according to this invention;

FIG. 12 illustrates a flow-chart outlining a method for determining anoverlay shift according to this invention;

FIG. 13 illustrates a flow-chart outlining a method for determining anoverlay shift according to this invention; and

FIG. 14 illustrates an electrical diagram of an overlay shiftdetermination structure according to this invention.

DETAILED DESCRIPTION

Electrical characteristics of an overlay shift determination structureare obtained, for example, by using wafer testers and wafer probersconnected to the probe members of the overlay shift determinationstructure. For example, the probe members of the overlay shiftdetermination structure are connected to electrical test structures andwafer testers in order to make electrical device characterizations. Anumber of different types of wafer testers and wafer probers can beutilized and are contemplated with the present invention, none of whichare limiting factors for the present invention. Wafer testers, such as,for example, HP4062 (200 mm) and HP4073 (300 mm) may be used. Each ofthese exemplary testers comprise a computer with 4 gigabytes of harddisk space and 128 megabytes of system memory.

The test instrumentation includes a parametric analyzer, such as, forexample, an HP-4142, a capacitance meter, such as, for example, anHP-3458A, a digital multi meter, such as, for example an HP-3458, and aninety-six position switch matrix. The HP-4142, for example, containsfour source-measurement units, two voltage monitors, two voltagesources, and a differential voltmeter. The source measurement units cansource up to 100 volts and 100 mA. Low current measurements may be downto a level of about 15 pA. It should be understood that the wafertesters disclosed above are provided for illustrative purposes and donot limit the present invention to such wafer testers.

As to wafer probers, KLA model 1200″s, KLA model ElectroGlas 4085″s andTSK UF200″s, for example, may be used with the various systems andmethods according to this invention. These probers can automaticallyprobe two cassettes of 25 wafers each. The wafer probers include athermo-chuck which allow elevated temperature measurements to about 200degrees Celsius. Such wafer probers may be used with the embodiments ofthe systems and methods according to this invention. It should again beunderstood that the wafer testers and/or probers disclosed above areprovided for illustrative purposes and do not limit the presentinvention to such wafer testers.

Now referring to FIG. 1, an electrical overlay shift determinationstructure 100 according to this invention is shown. The electricaloverlay shift determination structure 100 has a plurality of probemembers A, B, C, D and an electrical overlay target 110. Each of theprobe members A, B, C, D overlaps at least a portion of the electricaloverlay target 110. In this embodiment, four probe members are shown butthree or more probe members are also contemplated for use with thepresent invention. The four probe members A, B, C, D are in a firstlayer and the electrical overlay target 110 is in a second layer, andthe probe members are in electrical contact with the electrical overlaytarget 110. Similarly, as shown in FIGS. 4–6, the overlay target may bein the first layer and the probe members may be in the second layer.

In the embodiment of the overlay shift determination structure shown inFIGS. 1–3, at least the first layer of the overlay shift determinationstructure 100 is symmetrical about both the X and the Y axes of thefirst layer. The overlay shift determination structure which is shown inFIGS. 1–3 is properly aligned. In FIG. 1, line II—II represents theX-axis of the first layer and line III—III represents the Y-axis of thefirst layer. As shown in FIG. 1, the distance between an innermost point130 along an outside border of the first probe member A, which overlapswith the overlay target 110, and an innermost point 140 along an outsideborder of the second probe member B, which overlaps with the overlaytarget 110, is the same as the distance between an innermost point 150along an outside border of the third probe member C and an innermostpoint 160 along an outside border of the fourth probe member D. However,as discussed below, it should be understood that it is not necessary forthe first layer of the overlay shift determination structure 100 to besymmetrical about both the X and the Y axes of the first layer.

FIGS. 2 and 3, showing cross sectional views along lines II—II andIII—III, respectively, show the overlap length of the probe members A,B, C, D with the overlay target 110 being equal or substantially equal.That is, for example, the overlap length for each probe member along theY-axis is W_(o) and the overlap length for each probe member along theX-axis is W_(o). Further, as shown in FIGS. 1–3, the width of each ofthe probe members A, B, C, D is substantially, and in an embodiment,completely identical. Thus, when the overlap length of the probe membersA, B, C, D with the overlay target 110 is substantially, and in anembodiment completely, identical (i.e., when the first layer and thesecond layer of the overlay shift determination structure are properlyaligned), the contact area of each of the probe members with the overlaytarget is substantially, and in an embodiment, completely identical.

FIGS. 1–3 illustrate an embodiment of an overlay shift determinationstructure according to this invention where the first layer and thesecond layer of the overlay shift determination structure is properlyaligned. More particularly, as shown in FIGS. 1–3, the overlap area ofeach of the probe members A, B, C, D are substantially situated aboutthe X and Y axes of both the first layer and the overlay target, thusshowing proper alignment. However, as discussed below, if the first andsecond layers are improperly aligned, the probe members A, B, C, D aresubstantially symmetrically situated about the X and Y axes of the firstlayer, but the probe members A, B, C, D are not symmetrically situatedabout the X and Y axes of the overlay target.

The contact resistance of each probe member A, B, C, D with the overlaytarget is dependent on the contact area (i.e., the portion of the probemember which overlaps the overlay target). In this exemplary embodiment,when the first layer and the second layer of the overlay shiftdetermination structure are properly aligned, the contact of each probemember A, B, C, D with the overlay target 110 are substantially, and inan embodiment completely, identical. By having such an overlay shiftdetermination structure with four probe members, for example, which eachhave substantially, and in an embodiment, completely identical contactareas with the overlay target, only 3 measurements need to be made andthe calculations for determining the amount of misalignment are easier.

However, in another exemplary embodiment of this invention having fourprobe members, for example, the contact area for each pair of probemembers aligned along an axis may be substantially, and in anembodiment, completely identical when the first layer and the secondlayer of the overlay shift determination structure are properly aligned.Similarly, in another exemplary embodiment of this invention havingthree probe members, at least the contact resistance of the two probemembers aligned along a first axis should be substantially, and in anembodiment, completely identical.

Irrespective of the actual embodiment of the overlay shift determinationstructure, however, the contact resistance of the probe members when thefirst layer and the second layer are not properly aligned is used todetermine the amount of misalignment between the first and second layersof the overlay shift determination structure.

By having a first layer which is substantially symmetrical about theX-axis and the Y-axis, the total contact resistance across each of theaxes is the same irrespective of whether or not the first layer and thesecond layer of the overlay shift determination structure are properlyaligned. Thus, as set forth above, it is possible to determine both theX and Y translation/misalignment errors with only three measurements. Bymeasuring three voltages, it is possible to determine the resistancesacross three of the probe members based on the known applied currents.It should be understood by one of ordinary skill in the art that thecurrents applied to determine the voltages across each pair of probemembers, for example, may be the same amount or a different amount.Also, by determining at least three resistances across three differentpairs of probe members, it is possible to determine the resistances ofeach of the overlap areas (i.e., contact areas) of each probe membersand the overlay target 110 by solving four equations using three knownvalues and one unknown variable.

The following example of a method for obtaining the overlay shift amount(i.e., the misalignment amount) may be carried out in any order ofmeasurement and to any combination of the probe members. In addition, itshould be understood that the applied currents, for example I_(AB),I_(CD) may be the same or different. For example, it is possible todetermine both the X and Y translation errors by (1) applying a currentI_(DA) through D and A and measuring the voltage across B and C todetermine the resistance across B and C (i.e., R_(BC)); (2) applying acurrent I_(AB) through A and B and measuring the voltage across C and Dto determine the resistance across C and D (i.e., R_(CD)); (3) applyinga current I_(CD) through C and D and measuring the voltage across A andB to determine the resistance across A and B (i.e., R_(AB)); and (4)solving the following matrices to determine the resistances (R_(A),R_(B), R_(C), R_(D)) of each of the overlapped regions of the probemembers and the overlay target (110).

${\begin{bmatrix}1 & 1 & 0 & 0 \\0 & 1 & 1 & 0 \\0 & 0 & 1 & 1 \\1 & {- 1} & 1 & {- 1}\end{bmatrix}\begin{bmatrix}R_{A} \\R_{B} \\R_{C} \\R_{D}\end{bmatrix}} = \begin{bmatrix}R_{AB} \\R_{BC} \\R_{CD} \\0\end{bmatrix}$

The above matrix applies when resistances R_(AB), R_(BC), and R_(CD) aremeasured. If a different combination of resistances are measured asimilar matrix may be used. It should be understood by one of ordinaryskill in the art that the present invention is not intended to belimited by the matrices shown herein. It should be understood that oneskilled in the art could vary the equations contained in the matricesbased on the known variables. The resistances R_(A), R_(B), R_(C), R_(D)determined by solving the above matrices are then used to determine themisalignment along the X-axis O_(X) and/or the misalignment along theY-axis O_(Y) using the following equations:

$\begin{matrix}{O_{X} = {\frac{R_{o}w_{o}}{2}\left( {\frac{1}{R_{B}} - \frac{1}{R_{D}}} \right)}} \\{O_{Y} = {\frac{R_{o}w_{o}}{2}\left( {\frac{1}{R_{A}} - \frac{1}{R_{C}}} \right)}}\end{matrix}$where:

$R_{0} = {\frac{\left( {R_{A} + R_{C}} \right)}{2} = \frac{\left( {R_{B} + R_{D}} \right)}{2}}$

The embodiment is described above with four probe members. However, itis possible, for example, to have an overlay shift determinationstructure 100 according to this invention with three probe members. If athree probe member overlay shift determination structure is used it ispossible to determine the translation error along either the X-axis orthe Y-axis. For example, with an overlay shift determination structurehaving three probe members A, B, C shown in FIG. 1, it is possible todetermine the translation error along the Y-axis O_(Y).

The contact resistance between probe member and the overlay target 110is obtained by: (1) passing current I_(AC) through probe member A andprobe member C and measuring the voltage across at least one of A and Cor A and B to determine R_(A); (2) passing current I_(CA) through C andA and measuring the voltage across at least one of A and C or C and B todetermine R_(C); and (3) solving the following matrices to determine thevalues for the contact resistance of each probe member A, B, C with theoverlay target:

${\begin{bmatrix}1 & 1 & 0 \\0 & 1 & 1 \\1 & 0 & 1\end{bmatrix}\begin{bmatrix}R_{A} \\R_{B} \\R_{C}\end{bmatrix}} = \begin{bmatrix}R_{AB} \\R_{BC} \\R_{AC}\end{bmatrix}$

The resistance R_(AC) across probe members A and C may be measured orcalculated based on the known resistance across the axis, for example.With the determined contact resistances R_(A), R_(B), R_(C), thefollowing equation may be used to determine the misalignment along theY-axis O_(Y):

$O_{Y} = {\frac{R_{o}w_{o}}{2}\left( {\frac{1}{R_{A}} - \frac{1}{R_{C}}} \right)}$where:R _(o)=(R _(A) +R _(C))/2,

O_(Y) (nm) is the translation error along the Y-axis; R_(o) (ohm/cm²) isthe designed ohmic contact resistance, w_(o) (nm) is the designedoverlap; R_(A) (ohm/cm²) is the contact resistance on arm A, R_(B)(ohm/cm²) is the contact resistance on arm B and R_(C) (ohm/cm²) is thecontact resistance on arm C in order to calculate the translation errorin the Y-direction O_(Y). A similar process can be carried out todetermine the translation error in the X-direction.

If, as discussed above, the patterned masks are properly aligned withthe respective materials, the overlay shift determination structure 100is perfectly aligned such that the length of the overlap regions of eachof the probe members A, B, C, D with the electrical overlay target 110is substantially the same, as shown in FIGS. 1–6. For example, as shownin FIG. 2 the probe members A, B, C, D overlap the electrical overlaytarget by an identical length W_(o).

However, depending on the direction of misalignment, the length ofoverlap of the probe members situated along one axis and/or the lengthof overlap of the probe members situated along both axes may bedifferent. For example, as shown in FIG. 8, if the first layer isshifted an amount O_(x) in the X-direction, then the length of overlapof probe member D is W_(o)+O_(X) and the length of overlap of probemember B is W_(o) O_(X). Similarly, as shown in FIG. 9, if the firstlayer is shifted an amount O_(Y) in the Y-direction, then the length ofoverlap of probe member A along the Y-axis is W_(o)+O_(Y) and the lengthof overlap of probe member C is W_(o) O_(Y).

Referring still to FIGS. 1–3, the probe members A, B, C, D are in alayer which is situated above the layer in which the electrical overlaytarget 110. However, the overlay shift determination structure 100 issimilarly operative if the probe members A, B, C, D are in a layer whichis situated below the layer in which the electrical overlay target 110exists, as shown in FIGS. 4–6.

The probe members in the embodiments of the systems and methodsaccording to this invention may be of any size. However, the probemembers should be as small as possible to keep the size of the overlayshift determination structure as small as possible. In the variousexemplary embodiments of the systems and methods according to thisinvention, the size of the probe members A, B, C, D depend on theresolution capability of the lithography process used. For example, theprobe members may be lines having a width of about 200 nm.

Additionally, in the embodiments of the systems and methods according tothis invention, the probe members A, B, C, D and the electrical overlaytarget 110 can be made, for example, of doped n/p-Si, Tungsten, dopedpoly-Si, or other doped semiconductor materials, such as, for example,SiGe, GaAs, or other III–V semiconductors. Although the material for thefirst layer will usually be different from the material of the secondlayer, it is possible, for example, to have a overlay shiftdetermination structure according to this invention in which the probemembers A, B, C, D and the overlay target 110 are made of the samematerial. The material selected for the probe members A, B, C, D and/orthe electrical overlay target 110 should allow for the measurement ofthe contact resistance between the probe members and the electricaloverlay target. High resistance contact materials which have aresistance which is higher than the resistance caused by probing is usedfor the probe members A, B, C, D and the electrical overlay target 110.

FIGS. 7–9 show an embodiment of an overlay shift determination structurewhich is not properly aligned. However, as discussed above, due to thesubstantially symmetrical first layer, the total resistance across eachaxes of the overlay shift determination structure remains thesubstantially the same whether or not the overlapping region of eachprobe member is the same. As discussed above, when the first layer andthe second layer are not properly aligned, the overlapping areas of atleast two of the probe members A, B, C, D which are situated on the sameaxis are not substantially equal. Due to this misalignment, the contactarea of each of the probe members A, B, C, D with the electrical overlaytarget 110 changes, and thus the resistance resulting from theoverlapping condition changes. The amount of change of each of thecontact areas depends on the extent of the misalignment. As shown inFIG. 7, due to the improper alignment of the layer having the probemembers A, B, C, D with the layer having the electrical overlay target110, the contact length of probe member D is W_(o)+O_(X), the contactlength of probe member B is W_(o) O_(X,) the contact length of the probemember A is W_(o) +O_(Y) and the contact length of the probe member C isW_(o)−O_(Y).

FIG. 10 illustrates schematic views of an overlay shift determinationstructure according to this invention. The resistors R_(A), R_(B),R_(C), R_(D) represent the respective contact resistance between each ofthe probe members A, B, C, D and the electrical overlay target 110. Theresistors R_(AB), R_(BC), R_(CD), R_(DA) represent the resistancesacross each of the corresponding pairs of probe members. At least threeof the R_(AB), R_(BC), R_(CD), R_(DA) are measured by applying a currentI_(AB), I_(BC), I_(CD), I_(DA) across at least three respective pairs ofprobe members (i.e., for example, across probe members A and B forcurrent I_(AB)) and measuring the resistance across the other two probemembers. For example, if current is applied across probe member A and B,the voltage across probe members C and D is measured to determine theresistance across probe member C and D (i.e., R_(CD)). Thus, forexample, to determine the resistance across two adjacent probe members,current is applied to the other two probe members and the voltage ismeasure across the two adjacent probe member in order to determine theresistance across the two adjacent probe members. By measuring theresistances across R_(AB), R_(BC), and R_(CD) it is possible todetermine the contact resistances between each probe member and theoverlay target, that is, R_(A), R_(B), R_(C), R_(D) by solving thefollowing matrices:

${\begin{bmatrix}1 & 1 & 0 & 0 \\0 & 1 & 1 & 0 \\0 & 0 & 1 & 1 \\1 & {- 1} & 1 & {- 1}\end{bmatrix}\begin{bmatrix}R_{A} \\R_{B} \\R_{C} \\R_{D}\end{bmatrix}} = \begin{bmatrix}R_{AB} \\R_{BC} \\R_{CD} \\0\end{bmatrix}$

As discussed above, the alignment error along the X-axis O_(X) and/orthe Y-axis O_(Y) can be determined by solving the following equations

$\begin{matrix}{O_{X} = {\frac{R_{o}w_{o}}{2}\left( {\frac{1}{R_{B}} - \frac{1}{R_{D}}} \right)}} \\{O_{Y} = {\frac{R_{o}w_{o}}{2}\left( {\frac{1}{R_{A}} - \frac{1}{R_{C}}} \right)}}\end{matrix}$

where O_(Y) (nm) is the translation error along the Y-axis; O_(X) (nm)is the translation error along the X-axis; Ro (ohm/cm²) is the designedohmic contact resistance, W_(o) (nm) is the designed overlap; R_(A)(ohm/cm²) is the contact resistance on arm A, R_(B) (ohm/cm²) is thecontact resistance on arm B, R_(C) (ohm/cm²) is the contact resistanceon arm C, and R_(D) (ohm/cm²) is the contact resistance on arm D inorder to calculate the translation error in the Y-direction O_(Y) and/orthe translation error in the X-direction O_(X).

FIG. 11 illustrates a flow-chart outlining a method for determining anoverlay shift according to this invention. The steps of FIG. 11 (andFIG. 12) may represent a high level block diagram of the presentinvention. FIG. 11 (and FIG. 12) is based on the schematicallyrepresentative structure of FIG. 10. Additionally, the steps of FIG. 11(and FIG. 12) may be implemented on computer program code in combinationwith the appropriate hardware. This computer program code may be storedon storage media such as a diskette, hard disk, CD-ROM, DVD-ROM or tape,as well as a memory storage device or collection of memory storagedevices such as read-only memory (ROM) or random access memory (RAM).Additionally, the computer program code can be transferred to aworkstation over the Internet or some other type of network and may bestored in a database.

resistance R_(AB). In step 1120, current I_(DA) is passed from probemember D to probe member A and a second voltage V_(BC) is measuredacross probe member B and probe member C in order to determine a secondresistance R_(BC). In step 1130, current I_(AB) is passed from probemember A to probe member B and a third voltage V_(CD) is measured acrossprobe member C and probe member D in order to determine a thirdresistance R_(CD).

In step 1140, the resistance of each overlapping region of each probemember and the overlay target is determined. The measured resistancesR_(CD), R_(AD), R_(AB) are used to determine the contact resistancesR_(A), R_(B), R_(C), R_(D) by solving the matrices set forth above. Instep 1150, the contact resistances R_(A), R_(B), R_(C), R_(D) are usedto determine the amount of misalignment by solving the either or both ofthe equations set forth above. In step 1160, the process ends.

FIG. 12 illustrates a flow-chart outlining another method fordetermining an overlay shift according to this invention. In step 1200,the process starts. In step 1210, current I_(AB) is passed from probemember A to probe member B and a first voltage V_(CD) is measured acrossprobe member D and probe member C in order to determine a firstresistance R_(CD). In step 1220, current I_(BC) is passed from probemember B to probe member C and a second voltage V_(AD) is measuredacross probe member A and probe member D in order to determine a secondresistance R_(AD). In step 1230, current I_(CD) is passed from probemember C to probe member D and a third voltage V_(AB) is measured acrossprobe member A and probe member B in order to determine a thirdresistance R_(AB). In step 1240, current I_(DA) is passed from probemember D to probe member A and a third voltage V_(BC) is measured acrossprobe member B and probe member C in order to determine a thirdresistance R_(BC). In step 1250, the resistance of the overlapping areasof each probe member with the overlay target are determined using thefollowing matrices:

$O_{Y} = {\frac{R_{o}w_{o}}{2}\left( {\frac{1}{R_{A}} - \frac{1}{R_{C}}} \right)}$

In step 1260, the misalignment along the X-axis and/or the Y-axis isdetermined using the determined contact resistances and the equationsset forth above. In an optional step 1270, it is possible to determinean error term by using known methods of solving for an overdeterminedlinear structure. As shown in FIG. 12, the contact resistances of thefour probe members can be determined In step 1280, the process ends.

FIG. 13 illustrates a flow-chart outlining another method fordetermining an overlay shift according to this invention. In step 1300,the process starts. In step 1310, current I_(AB) is passed from probemember A to probe member B and a first voltage V_(CD) is measured acrossprobe member D and probe member C in order to determine a firstresistance R_(CD). In step 1320, current I_(BC) is passed from probemember B to probe member C and a second voltage V_(AD) is measuredacross probe member A and probe member D in order to determine a secondresistance R_(AD). In step 1330, current I_(CD) is passed from probemember C to probe member D and a third voltage V_(AB) is measured acrossprobe member A and probe member B in order to determine a thirdresistance R_(AB). In step 1340, current I_(DA) is passed from probemember D to probe member A and a third voltage V_(BC) is measured acrossprobe member B and probe member C in order to determine a thirdresistance R_(BC). In step 1350, current I_(AC) is passed from probemember A to probe member C in order to determine a fifth resistanceR_(AC) by measuring the voltage V_(AC) across probe member A and probemember C to determine R_(AC). In step 1360, current I_(BD) is passedfrom probe member B to probe member D and a sixth voltage V_(BD) ismeasured across probe member B and probe member D in order to determineR_(BD). In step 1370, the resistance of the overlapping areas of eachprobe member with the overlay target are determined using the followingmatrices:

${\begin{bmatrix}1 & 1 & 0 & 0 \\0 & 1 & 1 & 0 \\0 & 0 & 1 & 1 \\1 & 0 & 0 & 1 \\1 & 0 & 1 & 0 \\0 & 1 & 0 & 0 \\1 & {- 1} & 1 & {- 1}\end{bmatrix}\begin{bmatrix}R_{A} \\R_{B} \\R_{C} \\R_{D}\end{bmatrix}} = \begin{bmatrix}R_{AB} \\R_{BC} \\R_{CD} \\R_{AD} \\R_{AC} \\R_{BD} \\0\end{bmatrix}$

In step 1380 the misalignment along the X-axis and/or the Y-axis isdetermined using the determined contact resistances and the equationsset forth above. In step 1390, it is possible to determine an error termby using known methods of solving for an overdetermined linearstructure. In step 1400, the process ends.

FIG. 14 illustrates an electrical diagram of an overlay shiftdetermination structure according to this invention. As shown in FIG.14, a plurality of overlay shift determination structures according tothis invention may be used together in combination with a decoder 1410.As shown in FIG. 14, each of the probe members A, B, C, D are connectedto each one of the plurality of overlay shift determination structures.The decoder allows for the selection of the overlay shift determinationstructure to be used.

The systems and methods according to this invention can be manufacturedthrough standard microelectronic processes and can be integrated atseveral levels. For example, the shift overlay determination structureaccording to this invention can be provided to determine the alignmentbetween any two layers of a semiconductor device.

While this invention has been described in conjunction with theembodiments outlined above, it is evident that many alternatives,modifications and variations will be apparent to those skilled in theart. Accordingly, the above-described-exemplary embodiments of systemsand methods according to this invention, are intended to beillustrative, not limiting. Various changes may be made withoutdeparting from the spirit and scope of this invention.

1. An overlay shift determination structure comprising: a plurality ofprobe members in a first layer, the first layer including a first axisand a second axis perpendicular to the first axis, a first probe memberand a second probe member of the plurality of probe members beingdisposed along a first axis and a third probe member of the plurality ofprobe members being disposed perpendicular to the first probe member andthe second probe member, a fourth probe member of the plurality of probemembers being disposed perpendicular to the first probe member and thesecond probe member; and an overlay target in a second layer, at least aportion of each probe member of the plurality of probe members partiallyoverlapping and being connected to the overlay target, wherein a currentis applied across at least three pairs of probe members, wherein eachpair of probe members comprises two of the first probe member, thesecond probe member, the third probe member and the fourth probe member;and a voltage is measured across at least three pairs of probe members.2. The overlay shift determination structure according to claim 1,wherein each of the first layer and the second layer is a highresistance contact material.
 3. The overlay shift determinationstructure according to claim 2, wherein the high resistance contactmaterial is at least one of doped n-type Si, doped p-type Si, Tungsten,doped poly-Si, doped SiGe, doped GaAs.
 4. The overlay shiftdetermination structure according to claim 1, wherein the first layer ispositioned directly above the second layer.
 5. The overlay shiftdetermination structure according to claim 1, wherein the second layeris positioned directly below the first layer.
 6. The overlay shiftdetermination structure according to claim 1, wherein: the current issequentially applied across at least three pairs of probe members whichare adjacent to each other; and the voltage is sequentially measuredacross at least three pairs of probe members at a time when the currentis not being applied to the probe members in the pair across which thevoltage is being measured at the time.
 7. The overlay shiftdetermination structure according to claim 6, wherein: the current isfurther sequentially applied across at least one of the two pairs ofprobe members comprising probe members which are aligned along one ofthe first axis; and the second axis and the voltage is further measuredacross the pair of probe members across which the current is beingapplied at the time.
 8. The overlay shift determination structureaccording to claim 1, wherein the overlay shift determination structureis a plurality of overlay shift determination structures, wherein eachof the plurality of overlay shift determination structures determines anoverlay shift between any two layers of an integrated circuit.
 9. Theoverlay shift determination structure according to claim 8, furthercomprising a decoder, wherein the decoder is used to determine which ofthe plurality of the overlay shift determination structures is used. 10.An overlay shift determination structure comprising: a plurality ofprobe members in a first layer, the first layer including a first axisand a second axis perpendicular to the first axis, a first probe memberand a second probe member of the plurality of probe members beingdisposed along a first axis and a third probe member of the plurality ofprobe members being disposed perpendicular to the first probe member andthe second probe member, a fourth probe member of the plurality of probemembers being disposed perpendicular to the first probe member and thesecond probe member; and an overlay target in a second layer, at least aportion of each probe member of the plurality of probe members partiallyoverlapping and being connected to the overlay target, wherein: thethird probe member and the fourth probe member are substantiallysymmetrically situated along the second axis, and a total resistanceacross the first axis is equivalent to a total resistance across thesecond axis; and a distance between an innermost point along an outsideborder of the first probe member in contact with the overlay target andan innermost point along an outside border of the second probe member incontact with the overlay target is substantially equal to a distancebetween an innermost point along an outside border of the third probemember in contact with the overlay target and an innermost point alongan outside border of the fourth probe member in contact with the overlaytarget.